Gear support structure

Abstract

A gear support mechanism for supporting two gears and an intermediate gear which meshes with the two gears to transfer rotation of one of the two gears to the other, includes a gear-shaft support member(s) which supports a gear shaft of the intermediate gear; and a spring member installed between the gear-shaft support member and the intermediate gear. The spring member includes a gear contacting portion which is in contact with the intermediate gear, and resilient support legs extend radially from the gear contacting portion and are in contact with the gear-shaft support member, the spring member biasing the intermediate gear in a direction of an axis of the gear shaft. Each of the two gears is positioned in an inter-leg space between adjacent resilient support legs as viewed in a direction along the axis of the gear shaft.

What is claimed is: 
     
       1. A gear support mechanism for supporting two gears and an intermediate gear which meshes with said two gears to transfer rotation of one of said two gears to the other, said gear support mechanism comprising:
 at least one gear-shaft support member which supports a gear shaft of said intermediate gear; and 
 a spring member installed between said gear-shaft support member and said intermediate gear, 
 wherein said spring member includes a gear contacting portion which is in contact with said intermediate gear, and a plurality of resilient support legs which are resiliently deformable, extending radially from said gear contacting portion and are in contact with said gear-shaft support member, said spring member biasing said intermediate gear in a direction of an axis of said gear shaft by resiliently deforming said plurality of resilient support legs, and 
 wherein at least a part of each said two gears is positioned in an inter-leg space between adjacent resilient support legs of said plurality of resilient support legs as viewed in a direction along a central axis of rotation of said intermediate gear. 
 
     
     
       2. The gear support structure according to  claim 1 , wherein said plurality of resilient support legs are substantially the same in length from said gear contacting portion and arranged at substantially equi-angular intervals. 
     
     
       3. The gear support structure according to  claim 1 , wherein said gear-shaft support member comprises at least one anti-rotation portion which engages with said plurality of resilient support legs to prevent said spring member from rotating. 
     
     
       4. The gear support structure according to  claim 3 , wherein said gear-shaft support member comprises a cylindrical recessed portion for housing said intermediate gear, and
 wherein said anti-rotation portion includes a recessed portion formed on an inner wall of said cylindrical recessed portion. 
 
     
     
       5. The gear support structure according to  claim 1 , wherein said gear-shaft support member comprises:
 a gear-shaft forming portion from which said gear shaft of said intermediate gear projects; and 
 a retaining member which is fixed to said gear-shaft forming portion, supports an end of said gear shaft and prevents said intermediate gear from coming off said gear shaft, and 
 wherein said spring member is installed between said intermediate gear and one of said gear-shaft forming portion and said retaining member. 
 
     
     
       6. The gear support structure according to  claim 1 , wherein said gear contacting portion of said spring member is shaped into a ring having an opening into which said gear shaft is inserted. 
     
     
       7. The gear support structure according to  claim 1 , wherein said gear-shaft support member comprises two parallel plates which support both ends of said gear shaft, respectively. 
     
     
       8. The gear support structure according to  claim 1 , wherein said intermediate gear comprises a double gear including a small-diameter gear and a large-diameter gear which mesh with said two gears, respectively. 
     
     
       9. The gear support structure according to  claim 1 , wherein said plurality of resilient support legs extend from said gear contacting portion in radial directions obliquely away from said intermediate gear. 
     
     
       10. The gear support structure according to  claim 1 , wherein a free end of each said plurality of resilient support legs comprises a contacting end portion which lies in a plane substantially parallel to said gear contacting portion when said spring member is in a free state. 
     
     
       11. The gear support structure according to  claim 1 , wherein said two gears and said intermediate gear are elements of a gear mechanism for driving an autofocus lens group of an imaging device. 
     
     
       12. The gear support structure according to  claim 1 , wherein said gear shaft is integrally formed with said gear-shaft support member, and
 wherein a shaft hole, which rotatably supports said gear shaft, is formed in said intermediate gear. 
 
     
     
       13. The gear support structure according to  claim 1 , wherein said gear shaft is integrally formed with said intermediate gear, and
 wherein a shaft hole, which rotatably supports said gear shaft, is formed in said gear-shaft support member. 
 
     
     
       14. A gear support mechanism for supporting a gear train including a driving gear, a driven gear and an intermediate gear positioned between said driving gear and a driven gear to transfer rotational torque from said driving gear to said driven gear via said intermediate gear, said gear support mechanism comprising:
 two support members which hold said intermediate gear therebetween and support both ends of a gear shaft of said intermediate gear, respectively; and 
 a spring member installed between one of said two support members and said intermediate gear, 
 wherein said spring member includes a gear contacting portion which is in contact with said intermediate gear, and at least two resilient support legs which extend radially outwards from said gear contacting portion, radially outer ends of said two resilient support legs lying in a plane different from a plane in which said gear contacting portion lies and being in contact with said one of said two support members, and 
 wherein at least a part of said driving gear and at least a part of said driven gear are positioned inside of a circumscribing circle of said two resilient support legs about an axis of said gear shaft as viewed in a direction along a central axis of rotation of said intermediate gear.